Telephone



S.D.FIELD.

(No MQdel'.)

TELEPHONE.

Y No. 523,630.

Patented July 24, 1894.

UNITED STATES PATENT OFFICE,

STEPHEN D. FIELD, OF STOCKBRIDGE, ASSIGrNORv TO THE AMERICAN BELL b TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.l

TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 523,630, dated July 24, 1894. Application tiled April '7, ISM. Serial No. 506,696. (No model.)

.To all wle/0m it may concern,.-

le it known that I, STEPHEN D. FIELD, res1d 1ng at Stockbridge, in the county of Berkshlre and State of Massachusetts, have invented certain Improvements in Telephones, of which the following is a specification.

Thls invention relates to speaking telephones, and its object is to secure in one instrument the uniform action,and sharpness of operation, dependent upon the employment of thick diaphragme, andthe lightness and delicacy necessary for satisfactory operation, which has so far made requisite vibrating plates of diaphragme of extreme thinness.

Myimprovement is applicable to both transmitting and receiving telephones, and to those of the former class whether the diaphragm be employed to effectuate therequired changes of current by varying the resistance of a circult in which an electrical current from an independent source is alreadyk circulating, or by itself constituting or supporting the movable part of a generator, and thus when operated acting to set up a variable electrometive force, the resistance being constant.

As usually heretofore constructed, telephone diaphragms have consisted of a single, generally round, plate of metal or other suitable material clamped at the edges, or supported by spring pressure, and have been subjected to more or less stress by reason either of the attracting power of a magnet or of some mechanical device centrally applied.

I have ascertained that a combination of thin diaphragms may be made and so ar. ranged as to give all the magnetic conductivity, rapidity of motion, and accuracy of vibration incident to a thick vibrating plate, preserving at the Asame time the lightness and delicacy of action which are characteristic of thin plates.

My invention comprises a compound telephone diaphragm mounted on supports which permit free radial movement thereof, and which may for example be ball bearings; a diaphragm so constructed and mounted being applicable as an armature not to telephones only,but to electro magnets of any class; and comprises also a telephone combining such a peculiarly formed and arranged diaphragm vment of each plate, a contrivance of great or armature with its other essential elements and operating parts.

In attaining the object of my invention, I take two or more substantially similar diaphragms and rivet them together at their centers. I then separate or spring them apart at their edges, and maintain such separation by the interposition of balls of suitably hard material, such as metal, or ot' other similar mechanical appliance which will allow radial 6o movement of the diaphragrns when subjected to vibrations in `the usual manner, either by magnetic variation or by the impact of sound waves.

By way of illustrating the mechanical opl eration of the improvement We may profitably consider thel difference in result when equal forces are applied to a bar and fagot of iron of equal size, respectively, for the purpose of bending them.

' Let thehomogeneous barbeoneinchsquare, and one foot long, and let the-fagot be composed of one hundred plates, each one hundredth of an inch in thickness, one inch wide and twelve inches long. It is evident while the magnetic permeability of the two objects will be about the same, that the bar Will necessarily be extremely rigid and unyielding to the applied bending force, Whereas the fagot will relatively be yielding, and will show itself to be vastly superior to the bar in point of mobility.l

-When we consider the case of a fagot as above, wherein the separate laminae are in contact throughout their entire length, it is obvious that a considerable amount of fric- .tion will be encountered when the said fagot is bent,- owing to the sliding of each separate plate, over and upon the surface of its neighbors. If however the several plates of which it is composed be securelyfastened together at their centers, and seperated at their extremities by means of some medium which will allow of the separate longitudinal movemobility will be secured, which yet will possess all the magnetic conductivity or permeability of a solid bar.

In some instances when my compound diaphragm is associated with a magneto telerocv phone,I reinforce the magnetic conductivity of the arrangement by means of a supplemental iron or steel plate which should be of a Width suitable to be elciently acted upon by, orto act upon, the magnetic poles exposed to its influence.

The same principles, which, applied to telephones, approve the construction of a compound diaphragm having its component plates centrally united, but flared at their edges, and provided there with supports which permit radial movement, may evidently be applied to the armatures of many forms of electromagnets, and it is obvious that a compound diaphragm is when associated with the magnet of a magneto telephone, itself an armature, and is properly so termed.

In the drawings which accompany and illustrate the invention, Figure l is a longitudinal cross section of a magneto telephone embodying my invention. Fig. 2 is a section on the line 'y y of Fig. l looking toward the diaphragm which is partly broken away to more clearly show the radial supports. Fig. 3 is a central cross section of a variableresistance transmitter containing my invention; and Figs. 4, 5 and 6 are details thereof.

Referring to the type of instrument depicted by Figs. l and 2, B is the casing and C the cap piece of the telephone. They may be formed of any suitable material and united by a screw thread in the usual way, as shown, the latter having a cavity serving as a mouth or earpiece E with a central aperture 7c for the ingress and egress of the sound waves. M is the inducing magnet, in this case one with two active poles p, these being surrounded by helices or coils of wire c connecting by wires 2 and 3 with the screw terminals w and adapted thereby to be included in the telephone circuit. The space between the inner front surface of the cap piece and the shoulder o of the casing formsa chamber n of considerable depth within which the compound diaphragm D may be incased. I form this diaphragm of two plates CZ d2 rigidly united at their centers, but spread apart at their edges as indicated. If desired, an armature vl may be secured to the center of the inner surface of the diaphragm so as to be within the eld of force of the magnet, and in that event the diaphragm plates are not necessarily formed of magnetic metal. Fitted within the chamber o are the devices which support the diaphragm. The edge of the inner diaphragm d2, may rest on the shoulder o of the casing, and the said supports are mounted in any desired way between the edges of the two plates forming the compound diaphragm, in such a manner that as it vi brates whether under the influence of sound waves, or of magnetic variation, its plates may slide over the said radial supports, whereby the before recited advantages are secured. These supports in the present instance consist of a number of balls h of any suitable material loosely held in holes made in the web or Ilange f of a ring R, whose rim r is ftttedwithin the chamber o. When the instrument is constructed as described,the space g in front of the compound diaphragm forms the usual vocalizing chamber.

In the application of my invention disclosed in Figs. 3, it, 5 and 6, the diaphragm D is similarly made of constituent plates cl d2, and is contained with the other,working parts within a casing B supplemented by a cap C having the usual mouthpiece E. The diaphragm is organized to control contact electrodes, or a variable resistance of any form, that shown, being composed of a vibratory electrode V secured to the diaphragm center and acomplementary electrode W in constant contact therewith supported upon an adjustable screw passing through the Vback of the casing. The said screw serves also as the binding post @oto which the circuit wire 2 may be attached, and a second binding screw w is secured to the casing and is united internally by wire 3 to the diaphragm electrode and externally to the circuit wire 1t. The supports diifer in some respects from those of Figs. 1 and 2, being disk formed instead of spherical. The ring R has no inwardly projecting web or flange, but is provided with a number of pairs of hooks j. Between the t'wo hooks of each pair is mounted a disk or wheel b2; and these devices are placed at short distances apart, completely round the internal periphery of the ringand are mounted loosely on a circumferential wire or rod e which is supported in the bends of the hooks j. The operation of this form of instrument is not different from thatshown in the former figures.

It is evident that though I have in the foregoing examples described a compound diaphragm formed of but two constituent plates, a greater number may if desired be employed; and that instead of considering them when secured together at their centers as forming a single appliance, they may with equal propriety be regarded as a plurality of diaphragms independent, though centrally united.

I claiml. A compound telephone diaphragm formed of a plurality of constituent plates united at their centers, and separated or sprung apart at their edges the said edges being free to move radially, substantially as described.

2. In a'telephone, the combination of a compound diaphragm formed of a series of plates united at their centers, but otherwise independent, and bearing surfaces or supports for the edges of the separate plates which permit the free radial movement thereof, substantially as described.

3. The combination of a double or compound telephone diaphragm with free edges; and supports therefor, consisting of ball bearings interposed between the edges of the two members of the said double or compound dia phragm, substantially as described.

e, In an electromagnetic instrument for IOO transmitting producing or reproducing sound, a compound armature for an electro-magnet, formedas described herein, of laminae, cen.- trally united, and separated at their edges or extremities in such manner as to permit free and independent longitudinal movement.

5. An electrical speaking telephone comprising a magnet; helices surrounding the poles thereof; a compound diaphragm or armature for the said magnet formed of two independent plates rigidly united at their common center but separated at their edges; a flanged ring surrounding the said diaphragm; and a number of balls seated in perforations inthe iiange of said ring between the edges ot' the said compound diaphragm and serving as supports therefor.

6. In a telephone, the combination of a compound diaphragm, composed of a plurality of plates and anti-,friction bearing surfaces separating and supporting the edges of said plates, substantially as described.v

In testimony` whereof I have signed my naine to this specication, in the presence of two subscribing Witnesses, this 4th day of April, 1894.

. STEPHEN D. FIELD. Witnesses:

GEO. WILLIS PIERCE, FRANK C. LocKwooD. 

